Negative numbers

Negative numbers

Negative numbers are numbers below zero!

Examples of negative numbers are:

Temperatures in the winter. (brrr!)
Altitudes below sea level.

The numbers you call whole numbers will now be called positive whole numbers, (+1,+4,+5).

The positive whole numbers, the negative whole numbers and zero together are called integers.

You can picture integers on a number line, like this one:

 ...---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|...
      -7  -6  -5  -4  -3  -2  -1   0  +1  +2  +3  +4  +5  +6  +7  +8

You can think of adding and subtracting as moving along this line.
You move left to subtract, and you move right to add.

ADDING: Start at the first number and move right the second number of places:

Example: -3 +5

                       o----- 5 moves ----->
               start-> o---|---|---|---|---|
 ...---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|...
      -7  -6  -5  -4  -3  -2  -1   0  +1  +2  +3  +4  +5  +6  +7  +8
                                           ^
                                         answer! (+2)

SUBTRACTING: Start at the first number and move left the second number of places:

Example: +2 - 4

                           <--- 4 moves ---o
                           |---|---|---|---o <- start
 ...---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|...
      -7  -6  -5  -4  -3  -2  -1   0  +1  +2  +3  +4  +5  +6  +7  +8
                           ^
                        answer! (-2)

Note: when you start counting, start at zero and make your first move "one".